The invention relates to fixing devices, more particularly devices enabling individuals to fix articles to blockwork.
In this specification and in the claims appended hereto the term blockwork is to be taken to encompass aerated, foamed and the like building blocks of concrete or other materials which are usable in building and which are of a relatively more friable or porous nature than the majority of traditional building bricks.
In order to fix an article to a surface, for example a picture, shelf or cupboard to a wall it is necessary to provide for the secure fixing of the article to the surface.
If the surface is of wood this is relatively easily done by fixing the article to the surface with one or more pins, nails or wood screws.
If, as is more usual, one wishes to fix an article to brickwork or blockwork it is possible--for some light articles (e.g. pictures)--to make use of masonry pins and/or picture hooks comprising hardened steel nails or pins adapted to be driven by a hammer into the material of the surface.
If a heavier article is to be supported it is usual to pre-drill a hole in the wall, insert a plug into the hole in which a screw may be fitted; subsequent insertion of the screw in the plug causing it to expand and bear against the sides of the pre-drilled hole such that the screw and any article it supports is firmly held in the desired position.
Thus to fix articles to brickwork or blockwork generally requires the use of a drill with which to predrill a hole for a plug, which may be a disadvantage to the user in requiring him to obtain and make use of another tool.
Such arrangements work in the majority of cases, however, problems can arise if the surface is blockwork of a relatively friable or porous nature (for example modern day breeze or equivalent foamed aerate concrete blocks).
With such blocks their friable nature has the effect that they tend to break up as a hole is drilled into them with the result that it is difficult to form the initial hole. Even if a relatively "clean" hole can be pre-drilled in such blockwork the sides of the hole tend to break up as a screw forces the expansion of any plug placed in the hole.
For relatively light articles the friable nature of the blocks prevents the efficient use of masonry pins and the like--the material of the blocks tending to break-up as the pin is driven into it.